Document belt vacuum manifold

ABSTRACT

In a document handling system in which documents are moved on an apertured belt over a vacuum manifold to an imaging station of a copier, the vacuum manifold surface engaging the backside of the belt contains narrow, spaced apart, shallow grooves extending in the direction of movement of the belt. Vacuum is applied to the belt only through these grooves, to reduce belt/manifold friction. These manifold surface grooves have light reflective bottom surfaces closely spaced below the back of the belt to underlie the belt apertures and reduce their printout through translucent documents. The apertures in the vacuum belt are only in narrow bands overlying the grooves in the vacuum manifold. The apertures in the vacuum manifold are also preferably transversely spaced from the vacuum belt apertures so that they are not aligned during the belt movement.

Cross-reference is made to related applications with the same filingdate and Assignee, Ser. Nos. 111,051; 111,058; 111,059; 111,060;111,062; and 111,063. These cross referenced cases and the art citedherein are incorporated by reference to the extent appropriate.

For the faster xerographic and other document copiers now in commercialuse, it is increasingly desirable to provide for automatic handling ofthe individual original documents being copied in order to utilize thosehigher speed copying capabilities. However, such documents can varywidely in sheet size, weight, thickness, material, condition, humidity,age, and value. The documents may have curls, wrinkles, tears,"dog-ears", cut-outs, overlays, paste-ups, tape, staples, adhesiveareas, or other irregularities. Yet it is desirable to be able tosemi-automatically or automatically copy a set of documents with amixture of sizes, types, and conditions, without document jams ordocument damage. Further, it is desirable to handle such documents witha relatively compact and inexpensive document handling system.Preferably the document handling system is one which may be positionableover an existing or conventional external transparent copying platen(window) of a copier, and which can utilize the same existing orconventional optics system. That is, it is desirable that the automaticdocument handling system be readily removable from the platen area bythe copier operator whenever desired to allow for conventional manualcopying of documents, such as books, on the same copying platen.

One of the most important, and difficult to achieve, requirements forautomatic or semi-automatic document handling is the accurate andreliable, but safe, transporting and registration of the originaldocument at the proper position for copying. The document shouldnormally be precisely center registered or corner registered (dependingon the copier) over the copier platen. This registration accuracy isdesirably consistently within less than a millimeter. If the document isnot properly registered, or slips after registration, undesirable darkborders and/or edge shadow images may appear on the ensuring copy,and/or information near edges of the original documents may be lost,i.e., imaged beyond the edges of the copy sheet or not imaged.

Known document handling systems include various document transportswhich move the original documents over the platen. This may be a singleor multiple belt transport which utilizes frictional or electrostaticforces. However, it is known to be advantageous to have positive vacuumdetention or gripping of the document against the belt by vacuumapertures in the belt to avoid uncontrolled slippage or skewing of thedocument relative to the transport belt, as disclosed in U.S. Pat. No.4,043,665 issued Aug. 23, 1977 to John R. Caldwell, or U.S. Pat. No.4,008,956 issued Feb. 22, 1977 to Denis J. Stemmle. Other vacuum beltdocument transport publications include "Research Disclosure"Publications No. 16659, Feb. 1978; No. 17427, Oct. 1978; and No. 17809,Feb. 1979, published by Industrial Opportunities, Ltd., Havant,Hampshire, U.K..

It is also known to apply vacuum holding to a document for copyingthrough a plate or cover rather than through a moving transport belt, asdisclosed in a British application No. 42877/76 by L. D. Smith et al.,now U. K. specification 1532880, laid open May 12, 1978 in Japan aslaid-open No. 53-52436, and U.S. Pat. No. 3,245,291, issued Apr. 12,1966, to R. Wick et al..

While not designed for document handling for a copier, with appropriateoptical characteristics, etc., it is known to provide vacuum transportsfor sheets with ribs extending substantially above the vacuum aperturedsurface to distribute the vacuum under the sheet to be transported.Examples are shown in U.S. Pat No. 3,123,345 issued Mar. 3, 1964 to F.Ungerer; U.S. Pat. No. 3,452,982 issued July 1, 1969 to E. Bischoff;U.S. Pat. No. 3,477,558 issued Nov. 11, 1969 to F. J. Fleischauer andU.S. Pat. No. 3,583,614 issued June 8, 1971 to J. E. Foster. Multiplebelt copy sheet transports with vacuum applied in the spaces between thebelts are also known, e.g., U.S. Pat. No. 3,281,144 issued Oct. 25,1966, to L. H. Turner et al., and U.S. Pat. No. 3,743,403 issued July 3,1973 to F. J. Sanza.

It is also known to register the original document with roller nips orretractable or fixed registration gates in various ways. One way is topre-register the document to a vacuum belt with pre-registration fingersor rollers and move the document on the belt a known distance over theplaten into registration without slippage, as disclosed in theabove-cited patents. Another way is to provide retractable registrationfingers (or a fixed gate or stop edge) aligned with one edge of theplaten and engaging a frictional (non-vacuum) belt to normally stop anedge of the document being transported by the belt at the registrationposition overlying the platen, as disclosed in U.S. Pat. No. 3,910,570issued Oct. 7, 1975, to Charles D. Bleau, or various of the earlierreferences cited in the above Caldwell U.S. Pat. No. 4,043,665. In suchsystems the belt must slip relative to the document without damaging itonce the document has been stopped, at least briefly until the belt isstopped. The Bleau Pat. No. 3,910,570 also discloses rollers 32 engagingthe inside of the belt 17 between each pair of the gate fingers 29 toform localized bubbles or protrusions of the belt. (See FIG. 4 andColumn 4, lines 43 et. al., for example). U.S. Pat. No. 3,863,912 issuedFeb. 4, 1975, to R. D. Korff discloses a document belt with parallelridges extending around the belt in its direction of movement. It isknown that the document may be either driven forward into a downstreamplaten edge registration gate or reversed over the platen to back thedocument up against an upstream platen edge registration gate. It isalso known to register documents without such gates or other stops bysensing the passage of the lead or trail edge of the document with aphotodetector as it moves toward or past registration and driving thedocument belt forward or backward for a brief fixed distance or timethereafter without slippage of the document thereon, providing thedocuments are deskewed.

In these above-described systems where the document is on a moving belttransport but must be registered at a precise location by a registrationgate, to the belt or to a fixed position, there is a serious difficultyin avoiding the escape or slippage of the document from between the tipsof the registration gate fingers and the moving belt, particularly forcertain document weights and conditions (e.g., curled edges). Besidesloss of registration, such slippage can cause serious damage to theoriginal documents. Also, if a document is stopped by only one of two ormore spaced fingers it can become skewed. Besides mis-registration imageloss and edge or background effects this skewing can cause seriousproblems in the further transporting of the document.

If the document transport comprises a plurality of separate narrowdocument belts, the registration fingers can be extended up between thebelts to insure capture of the document edge. However, as noted in theabove-cited Bleau patent, such separate belts can produce backgroundstripes on the copies from the images or shadows of the belt edges whichare behind and adjacent the document. This is aggrevated by dirtcontamination of the belt edges.

Such "show-through" and/or "show-around" background printout on thecopies, respectively, is a general problem with various documenttransport belts. That is, when a document is imaged for copying againsta belt, any optically significant irregularities in the belt surface canbe copied also, to print-out on the copies as undesirable darkbackground areas. To avoid this problem, a single smooth, continuous andoptically uniform light reflective document belt surface larger than thelargest document to be copied thereon is preferred. Any edges,transitions or vacuum apertures in the belt in the exposure area canproduce shadows which "showthrough" translucent documents being copied,and/or "showaround" any mis-registered or undersized documents. Normaldirt contamination (darkening) of belt surface irregularities aggrevatesthese background problems.

Show-around problems and registration criticality can be reduced byslightly magnifying the document image to "overfill" the copy sheetarea, or by registering a document edge beyond the imaged area. However,both approaches sacrifice the non-imaged information near the edges ofthe document, and that loss is additive for copies of copies. Further,when reduction copying of a document is done (e.g., less than 1:1optical reproduction), or where the document is smaller than the copysheets, the image reproduced on the copy will include substantial areasof the belt which are within the now expanded original image area andthus beyond (outside the area of) the document. Thus, the potential"show-around" problem area is more extensive.

One partial approach to the "show around" problem is to not aperture thevacuum belt in narrow bands corresponding to the normal edge positionsof the documents as disclosed in U.S. Pat. No. 4,047,812 issued Sept.13, 1977 to James W. Hogan. However, as noted there, this results in novacuum holddown forces being applied to those areas of the document.Also, since the aperture pattern is otherwise continuous, the aperturesare still visible adjacent the lead and trail edges of the document.This Hogan patent, and the above-cited Caldwell patent, approach the"show through" problem by using small diameter vacuum apertures.However, as noted there, very fine holes are subjected to clogging bypaper lint and other contamination. They also provide increased airresistance and a smaller effective vacuum area, thereby increasing thepower requirements of the vacuum source to maintain desired vacuumacquisition and holding forces on the document. Another approach is touse a transparent vacuum belt with a light reflector behind the belt, asdisclosed in U.S. Pat. No. 4,120,579, issued Oct. 17, 1978, to D. J.Maiorano. However, scratches or dust on the belt can cause backgroundprint-out. U.S. Pat. No. 3,677,643 issued July 18, 1972 to B. K. Sagawateaches a vacuum document exposure drum with vacuum orifices recessedwithin reflective conical recesses to prevent orifice printout in anoverlay (contact print) copier.

The present invention is not limited to any particular type of documentillumination system, and is applicable to, for example, either scanninglamp stationary document copying or moving document stationary opticscopying (slit scanning). However, it is particularly suitable for fullframe flash illumination systems with light directed and reflected tothe document and document belt from all angles, since this assists ineliminating edge shadows. One such illumination system is disclosed inU.S. application Ser. No. 15,588 filed Feb. 26, 1979, now U.S. Pat. No.4,250,538 issued Feb. 10, 1981, by John A. Durbin et al. and its citedart.

The present invention overcomes or minimizes the above-discussedproblems in an original document handling apparatus for movingsuccessive individual document sheets on the surface of a movable beltinto a registered position for copying at a copier imaging station byproviding a document transport belt with vacuum grooves which are soconstructed as to appear optically smooth to the copier optics, yetwhich also provide improved document vacuum retention, and whichminimizes both show-through and show-around.

In the exemplary document handling system, disclosed in the followingspecification, in which documents are moved with a vacuum belt to animaging station of a copier, and where the documents are imaged on alight reflective principal document imaging surface on a first side ofsaid belt, and in which the documents are held against said first sideof said belt by an air flow applied from a vacuum manifold at the secondside of said belt through multiple vacuum apertures extending throughthe belt and opening on said first side, said first side of said belthas a multiplicity of shallow vacuum channels recessed below saidprincipal light reflective document imaging surface. These vacuumchannels have sufficiently gently sloping walls and light reflectivecharacteristics substantially equal to or better than said documentimaging surface to avoid imaged shadows thereof at said imaging station.These vacuum channels are pneumatically connected to said vacuumapertures but extend outwardly from and beyond the vacuum apertures oversaid document imaging surface of said belt. The openings of said vacuumapertures are disclosed as limited to areas of said first side of saidbelt coverable by the smallest document to be imaged thereagainst, toavoid show-around exposure of said apertures during document imaging.The openings of said vacuum apertures at said first side of said beltare recessed within said vacuum channels so that said vacuum apertureopenings are substantially spaced below said document imaging surface.Also, said vacuum channels are sufficiently narrow to prevent vacuumdeformation of flimsey documents directly against said openings of saidvacuum apertures, yet the openings of said vacuum apertures at saidfirst side of said belt are sufficiently large to provide a lowimpedance relatively unrestricted air flow therethrough relative to saidcross-sectional areas of said vacuum channels, so that documenthold-down force-generating air-flows can be drawn from the direction ofthe edge of the document through said vacuum channels under the documentand into said openings of said vacuum apertures, with a vacuum generatedin said channels between said document edge and said vacuum apertures,and so that neither said vacuum channels or said vacuum apertures aresubstantially imagable when a document is imaged on said documentimaging surface at said imaging station.

Additional disclosed features include providing of a minimum area ofsaid openings of said vacuum apertures greater than the minimumcross-sectional areas of their respective vacuum channels to which theyare pneumatically connected so that the predominant vacuum drop fromsaid air flow will occur in said channels under a document rather thanin said vacuum apertures, and wherein said channels may extend beyond atleast one dimension of the largest documents to be imaged on said beltto provide pneumatic edge hold-down forces.

Further features and advantages of the present invention pertain to theparticular apparatus whereby the above noted aspects and features of theinvention are attained. Accordingly, the invention will be betterunderstood by reference to the following description, including thedrawings forming a part thereof, wherein:

FIG. 1 is a cross-sectional side view of an exemplary document handlingsystem in accordance with the present invention;

FIG. 2 is a bottom view of the exemplary system of FIG. 1;

FIG. 3 is an enlarged partial cross-sectional view taken along the lines3--3 of FIG. 2;

FIG. 4 is an enlarged partial cross-sectional view taken along the lines4--4 of FIG. 2;

FIG. 5 is an alternative embodiment of the portion of the systemillustrated in FIG. 4;

FIG. 6 is a bottom view of an alternative document belt embodiment ofthe document handling system of FIGS. 1-4;

FIG. 7 is an enlarged partial cross-sectional view taken along the lines7--7 in FIG. 6; and

FIG. 8 is an enlarged central portion of FIG. 6, and its cross-sectionalside view on two orthogonal axies.

Referring first to FIGS. 1-4, they illustrate one example of the presentinvention. However, it will be appreciated that the invention may havemany other different structures or orientations, and combinations withvarious xerographic or other copying systems. FIGS. 5-8 and theabove-cited and other patents provide examples of further or alternativeapparatus.

Referring first to FIG. 1, there is shown an exemplary document handlingapparatus 10. This drawing is not to scale, as it is transverselyforeshortened for drawing clarity. That is, the document belt 12illustrated would be preferably relatively more elongated between itsend support and drive rollers 14 and 16. Further, while a semi-automaticdocument handling system for a copier is illustrated here forsimplicity, it will be appreciated that the invention is fullyapplicable to various recirculating document handling systems forpre-collation copying.

In the exemplary apparatus 10 of FIG. 1 there is illustrated a vacuummanifold 18 with an aperture plate 20 for applying a vacuum to thebackside of an apertured vacuum document belt 12, which vacuum isprovided by a blower 22. The document belt 12 and the plate 20 aremounted so that a document 23 may be transported on the document belt 12closely and evenly spaced (e.g., approximately 0.5 mm) above thetransparent platen 24 of the copier, where the document may be copiedwithin the depth of focus of the optical system of the copier throughthe platen 24.

Documents 23 here are inserted into the belt transport system at adocument input area or loading station 26 near the upstream end of thebelt 12, manually or automatically. The documents may then be ejectedfrom an output area 28 at the downstream end of the belt and the platen.Alternatively, the belt drive may be reversed to eject the document fromthe input area 26. It will be appreciated that various known sheetguides or baffles, and/or idler rollers engaging the belt 12, as shownat the input area 26, may be utilized to assist the document path ateither the input or output areas. Upstream pre-registration gates orrollers may also be provided.

Referring now to the registration of the documents 23 at the desiredcopying position on the platen 24, there are illustrated in FIG. 1 tworegistration gate systems; an upstream registration gate 30 and adownstream registration gate 32. These gates 30 and 32 have respectivesets of registration fingers 31 and 33 which are movable in and out ofthe path of the documents for their registration, i.e., toward and awayfrom cooperative engagement with the belt 12.

As indicated, there are various types of registration systems forsuccessfully registering individual document sheets on the surface ofthe belt 12 in the registration position for copying at the copierimaging or exposure station. For example only one, or both, or neither,of the registration gates 30 and 32 illustrated here may be utilized,and these gates may have different structures or be utilized indifferent manners.

Both of the illustrated registration gates 30 and 32 as well as the beltdrive "M" may be conventionally controlled by a timing control 34.Preferably the control 34 is incorporated in a general conventionalcentral copier microprocessor control with programming. Some examplesare disclosed In U.S. Pat. Nos. 4,062,061 issued Dec. 6, 1977 to P. J.Batchelor et al., U.S. Pat. No. 4,076,408 issued Feb. 28, 1978 to M. G.Reid et al., U.S. Pat. No. 4,078,787 issued Mar. 14, 1978 to L. E.Burlew et al., U.S. Pat. No. 4,099,150 issued July 4, 1978 to J. L.Conin; U.S. Pat. No. 4,125,325 issued Nov. 14, 1978 to P. J. Batcheloret al., and U.S. Pat. No. 4,144,550 issued Mar. 13, 1979 to J. K.Donohue et al. However, timing and control may be provided by anydesired conventional logic, such as commercial timing circuits, ormultiple lobe cams on a timing shaft, or any other suitable timingsystem which provides the desired sequence of operations.

The present invention is not limited to a particular registration systembut rather relates primarily to the unique construction and operation ofthe document belt 12 to be described hereinbelow. However, some examplesof the operation of possible registration systems will be brieflydiscussed. In one mode, the upstream registration gate 30 pre-registersthe document to a selected fixed position on the belt 12 upstream of theplaten and then the document is driven for a known fixed distance fromthat gate 30 downstream over the platen without slippage. Copying takesplace after this known advancement into the registration position, asdescribed in the above-cited U.S. Pat. No. 4,043,665. Note that in sucha system the downstream registration gate 32 is not required. However,if desired, it may be additionally provided for final orre-registration.

Alternatively, only the downstream registration gate 32 may be utilized,i.e., the document would not be pre-registered. In this case, thedocument is driven by the belt 12 over the platen until the lead edge ofthe document contacts the raised registration fingers 33, which arepositioned directly at the downstream (beveled) edge of the platen 24.Relative frictional slippage is then provided between the belt 12 andthe document so that the document may deskew and fully align against allthe registration fingers 33. For this, the document belt is run for atleast a brief period after the registration is achieved by thedownstream registration gate 32.

For this registration mode there is additionally illustrated here anintermittently operable vacuum control valve 35. This may be a solenoidactuated flapper valve controlled by the timing control 34, as shown, incoordination with one or both registration systems. Opening of the valve35 quickly reduces the vacuum in the manifold 18, and thereby reducesthe vacuum applied through the document belt 12 to allow slippagebetween the document and the belt during registration. Closing of thevalve 35 quickly restores the vacuum. This valve operation may also bedone during initial loading or pre-registration of the document onto thebelt 12 at the input area 26. If desired, the area to which such acontrolled vacuum may be applied may be a separate portion of a belt,i.e., a separate vacuum manifold chamber or section.

The downstream registration gate 32 is conventionally opened by itssolenoid or other actuator linearly pulling the registration fingers 33out of the path of the document. After the document is copied it maythen be ejected in either direction from the platen by the belt drive.The upstream registration gate 30 conventionally operates, as shown byits dashed line with arrows, by rotating in and out of the documentpath, with a clutch drive, cam, or solenoid.

Referring now to FIGS. 2, 3 and 4, the unique configuration of the belt12 will be described, with particular reference to the enlargedcross-sectional view of FIG. 3.

As shown in FIG. 2, the belt 12 has a plurality of narrow, elongated,permanent shallow grooves 36 in minor, spaced, document imaging areasthereof. These grooves 36 here extend linearly transverse the directionof movement of the belt. They are below the planar document transportingouter surface 37 of the belt. The grooves 36 are each narrower in width(the transverse dimension in FIG. 3) than the spacing across theintervening belt surface 37 between the grooves, and are not connectedtogether, so as to provide pneumatic separation. All of the grooves 36have smooth and gently sloped side walls 36a and are so configured as toavoid any reproducible shadows from the grooves at the copier imagingstation. That is, the side walls 36a are both at a gentle acute angle,preferably less than approximately 20°, from the document transportingsurface 37 so that there are no "edge shadows" from the sides of thegrooves. With improved optical cavity illumination the groove wall slopemay be somewhat greater than 20°. There are no sharp transistions oredges. The base 36b is preferably not greatly more than approximatelyone millimeter in depth below the surface 37, and preferably not greatlyless than approximately 0.2 millimeters deep. Thus, the preferredgrooves are effectively shallow and gentle slight undulations in thebelt surface. The groove surfaces preferably have substantially the sameor better reflective characteristics as the surface 37. The entiregroove 36, i.e., both sides 36a and the bottom or base 36b, are therebyfully and uniformly illuminated by the illumination system of thecopier. Thus, both show-through and show-around copy defects arenormally avoided, and substantially entirely eliminated for conventionaldocuments.

The width of the grooves 36, preferably less than approximately 5millimeters, is sufficiently narrow such that the beam strength of thedocument 23 prevents even a thin document from sagging or being pulledinto contact with the base 36b of the grooves 36, even when a vacuum isapplied to the grooves 36. Some slight corregation of light weightsheets partially into the grooves may be desirable, providing there isno loss of optical resolution or other image distortion. This increasesthe stiffness or beam strength of these thinner sheets, particularlyagainst bending on the orthogonal axis, and may assist theirregistration. Note that the grooves do not need to be provided acrossthe full width of the belt. They may extend somewhat less than the widthof the widest document to be transported or alternatively, somewhat more(note FIG. 2).

The lateral or transverse alignment of the belt 12 along the axes of therollers 14 and 16 and its drive may be accomplished in a known manner byuse of sprockets or "V" grooves on the rollers 14 and 16 mating withcorresponding sprocket holes or grooves along at least one edge of thebelt 12. Alternative known alignment or realignment systems or guides ofthe belt may be utilized.

A variety of materials and methods of fabrication may be utilized forthe belt 12. Preferably it is fabricated from an elastomeric low surfaceenergy flexible plastic or rubber material, with sufficient conductivityto avoid static electricity build-up. The overall belt thickness may beapproximately 0.4 to 1.5 millimeters. The belt with the grooves 36integrally formed therein may be continuously fabricated and then theappropriate belt length cut off and seamed to form an endless loop.Alternatively, the grooves can be machined, or the entire belt withgrooves monolithically formed by casting. If desired, the belt can havetwo or more layers of different material, such as a "Mylar" inelasticplastic substrate with an overcoating of white (light reflective) higherfriction elastomeric or other material providing the documenttransporting outer surface 37.

The vacuum belt 12 and its vacuum system provide vacuum retention of thedocument to the belt in a manner which avoids show-through orshow-around images of the vacuum holes in the belt 12 from beingreproduced on the copy sheets. However, it also provides improved, lowerpower, vacuum retention of the copy sheets. That is, both desiredfeatures are enhanced with this system rather than one feature beingsacrificed for the other. As shown in FIG. 2, multiple vacuum apertures40 are provided through the belt 12 opening only in the base area 36b ofthe grooves 36. That is, the vacuum apertures in the belt are open atthe image side of the belt, but recessed within the grooves 36,relatively large, and in the thinnest portions of the belt.

Placing the vacuum inlet holes 40 in the valleys or bottoms 36b of thegrooves moves them substantially out of contact with the document beingtransported. This serves to prevent show-through as long as the documenthas reasonable light diffusion characteristics. However, there is anequally important purpose. Since the document does not directly overlieand block the vacuum apertures, the grooves 36 distribute the vacuumfrom the holes along the grooves under the document and towards theedges thereof, as will be further explained. Further, each groove is aseparate, independent, vacuum area.

Preferably the vacuum holes 40 are located in discrete spaced groups 38around the belt circumference to which the documents are registered, sothat the vacuum holes will always be fully covered by the documentsduring imaging, to avoid show-around imaging of the holes. For example,by selection of the length of the belt and the size and spacing of thegroups or patterns of holes along the belt, two, three, or anotherintegral number, of discrete apertured and grooved areas 38 may beprovided for the number of documents to be fed per belt revolution. Forexample, assuming a 30 centimeter platen in the direction of beltmotion, three 37 centimeter pitches (spaced hole area patterns) 38 canbe provided with a belt 111 centimeters in circumference. That is, threehole groups could be provided equidistantly around the belt.

Only the area under the lead edge of the document to be captured need beapertured. Thus, for circumferential grooves the length of each holegroup in the direction of belt motion could be on the order of only 5centimeters and sixteen holes approximately 1.6 millimeters in diameterand approximately 3 millimeters apart, center-to-center, would beappropriate. In the exemplary transverse groove system of FIG. 2 thereare only ten holes 40 in each groove, one group of five holes near theregistration side, and the other group of five holes spaced 50 mmdistant, approximately in the middle of the belt, to underly thenarrowest document to be handled, thus forming two circumferential bandsof apertures. However, only the limited areas 38 of only, for example,twenty-five transverse grooves are apertured, so that each area 38,including its bands of apertures 40 only have 168 mm of circumferentiallengths on a 103.5 cm belt (in the direction of belt movement).

By selecting the pitch (spacing) and size of the hole and groovepatterns 38 so that an unapertured length of belt 39 is available whichis longer than the platen size, an unapertured and ungrooved area ofbelt may be automatically positioned over the platen during manualcopying. It will provide a continuous, completely smooth and unaperturedplanar background for any size of copy being manually copied, overlyingthe entire platen, as will be further described herein.

The "overhang" of the belt, i.e., its extension beyond the upstream anddownstream edges of the platen, may be utilized for the document inputarea 26 and output area 28. This additional document transporting by thesame system before and after copying may be desirably utilized tointegrate this system with input sheet feeders and output stackers orother transports. For example, with the above-described exemplary threepitch belt and 30 centimeter platen and 3.8 centimeter diameter pulleys,there is provided an approximately 9-10 centimeter overhang or extensionof the belt at each side of the platen.

As a preferred example, as in FIGS. 2-4, for a platen capable of fullframe imaging of large standard documents a 103.5 cm long endless belt12 between two 25.4 cm diameter pulleys may have two spaced imagingareas, i.e., two patterned belt surface areas 38, with, for example,each pattern 38 having approximately 25 parallel vacuum grooves 36extending linearly approximately 366 mm across the belt surface 37transverse the direction of belt motion and spaced approximately 7 mmapart, center line to center line, but with vacuum holes in only thosetwo minor areas of the total groove lengths which will be covered by thesmallest document to be transported. The vacuum apertures 40 through thebelt may be approximately 2.8 mm in diameter round holes perpendicularthe belt surface. The holes may be evenly spaced apart along the bottom(and center line) of the grooves by approximately 9.4 mm within theirabove-described two bands. The grooves themselves may be approximately4.6 mm wide at the belt imaging surface, and approximately 0.2 mm deep.The total belt thickness may be only approximately 0.45 mm. The shape ofthe grooves may be smoothly cylindrical to a much larger radius, e.g.,approximately 13.3 mm, to avoid any angular transitions which couldcause edge shadows. This also ensures, to the same end, a desired smallslope angle of less than 20 degrees, and preferably less than 10degrees, between the side walls of the grooves and the imaging surface.This low angle of incidence is an important feature. The transitionlines between the edges of the grooves and the imaging surface are alsopreferably rounded or smoothed to blend in or transition smoothly.

A relatively low power and low pressure vacuum system 22 may beutilized. For example, a manifold vacuum level of not substantiallygreater than 25 millimeters of water and an air flow of somewhat morethan only 1.8×10⁻³ cubic meters per second could be sufficient.

With the above-described system of discrete vacuum hole groups, to whichthe document is to be fully overlaid, it will be appreciated that thedocument is registered to a specific belt positions at the documentinput area 26. This may be accomplished by holding the document at thepre-registration gate 30 (or other preregistration gate) until a beltcursor 50, which may be holes or other indicia along the belt edge,actuates a photo-optical or other sensor 52 connected to the timingcontrol 34. The document is thereby released at the appropriate time forthe lead edge of the document to overlie the hole pattern and thedocument is then fed by the belt without slippage over the platen intoregistration. No over-platen registration is required. The same or otherfiduciary marks 50 and sensors 52 may be used to stop the belt at theregistration position (with the document positioned over the platen).

With the above described registration system, the document is registeredagainst the vacuum belt completely overlying one of the discrete minorvacuum aperture patterned areas 38 of the belt 12. The belt is thendriven, by a conventional servo motor "M", stepper motor, timed drivebraked motor, geneva drive, or the like, connecting with, or integral,belt drive roller 16, or 14. The apertured area 38 of the belt is thusdriven from the initial loading station, in which the pattern 30 isoverlayed with the document, into the exposure station of the copier.The initial registration or loading of the document overlying all (andhiding all) of the vacuum holes 48 of one entire pattern 38 ismaintained as the apertured area 38 is advanced to the exposure station.This will normally be the position in which the lead area of the vacuumaperture pattern 38 is adjacent the downstream or registration edge ofthe exposure platen 24 of the copier. The vacuum apertured areas 38 arein at least two discrete and minor areas of the belt which aresubstantially spaced circumferentially along the surface of the belt inthe direction of belt motion. The belt is unapertured and opticallysmooth and continuous between the spaced vacuum apertured area 38. Thespacing between the vacuum apertured area 38 is sufficiently great sothat when one vacuum pattern 38 has transported the document to theexposure station, no vacuum apertures are exposed to the copier opticsfor copying from any of the other vacuum apertured areas 38. That is,preferably, only one area or pattern of vacuum apertures 38 is overlyingthe platen at any time during which a document is being copied. This canbe accomplished by having the circumferential spacing between patternsbeing greater than the dimensions of the platen. However it will beappreciated that in some copiers, such as those with optical reduction,that the dimensions of the platen may be larger than the actualdimensions of the exposure area or exposure station for normal copying.Thus, the spacing along the belt between the vacuum apertured areas 38in such copiers for normal copying need only be equal or greater thanthe dimensions of the actual exposure station.

It has been additionally found that by appropriate spacing of the vacuumaperture 38 along the endless belt 12 circumference that spacing may besuch that one vacuum area 38 is in the document loading station, whileanother vacuum aperture 38 is in the exposure station. Thus, copying ofone document (without show-through or showaround of vacuum apertures)may be accomplished simultaneously with the registration loading of thenext document over the next vacuum area 38. This is particularlydesirable in a document handler in which the document is slowed down orstopped in the exposure position, since this allows the overlay anddeskewing of the next document to be accomplished during the same timedelay period the previous document is being copied, and with the beltstopped or slowed down. The belt then may be quickly accelerated anddecelerated to place this next document in the exposure station whilethe previous document is being either ejected from the document handleror restacked in the document stacker in the case of a recirculatingdocument handler.

It will be appreciated, as to the means for registering the loading ofthe document to the vacuum belt, that various known and suitable systemsmay be utilized. The system disclosed herein senses the presence andposition of one vacuum apertured area 38 in the proper position for theinfeeding of a document thereover by permanent marking indicia, such asholes, at predetermined positions along at least one edge of the beltoutside of the optical imaging station exposure of the belt. Thedocument registration then comprises feeding the document onto the beltin registration with the sensed position of the belt by startingdocument feed rollers or belts, and/or by releasing a registration gateholding the lead edge of the document as illustrated, or the like.However, it would also be possible to provide a loading registrationsystem in which the document is fed uninterruptedly over the belt, andwhen a document lead edge sensor determines that the lead edge of thedocument has been fed slightly past the most downstream vacuum aperturesof the pattern 38 to then acquire the document by pressing it againstthe belt and applying a vacuum and then start moving the belt.

With the belt configuration described herein, wherein the maximumdimensions of the apertured area 38 in any direction are smaller thanthe smallest conventional document to be transported and copied on thedocument belt 12, and wherein the belt surface is optically continuouslyuniform to the copier optics everywhere except for said vacuum apertures40, it will be appreciated that with the above-described system, inwhich the document is only placed on the belt so as to completely overlyone entire pattern of vacuum apertures 38, and wherein the spacingbetween the apertured areas 38 is as described above; that show-aroundcan be completely eliminated, because no vacuum apertures are everexposed to the copier optics and therefore cannot provide visibleprintout on any copies, for any of the sizes of documents being copied.However, as otherwise indicated herein, to be fully effective, there isalso employed the disclosed system for conveying a vacuum holding forcefrom these minor apertured areas 38 out under a much larger area of amuch larger document, if the document handling system is to have thecapability to handle a wide range of document sizes without slippage.This transverse extension of the effective vacuum area acting on thebackside of the larger document is provided by the vacuum groove systemdescribed herein without causing increased show-around problems forsmaller documents, because the grooves themselves, in their unaperturedareas, are effectively optically invisible to the copier in the imagingstation. The unapertured grooves have effectively the same lightreflective background characteristics as the major areas 39 of the belt(between the patterns 38) which are ungrooved.

As an additional feature, as indicated above, by the selection of theappropriate spacing between the minor hole and groove patterns 38, acompletely unapertured and ungrooved area 39 of the belt 12 may beprovided which is larger than the entire area of the platen 24. Byautomatically positioning this completely smooth and continuous lightreflective background over the platen whenever the document belt is notbeing used for automatic or semi-automatic document feeding, a platencover can be provided having the same background-free optical uniformityfor manual copying as is conventionally provided by the flexible whiterubber sheet platen covers of xerographic copiers which do not havedocument handlers.

By conventionally mounting the document handling unit 10 here pivotablyover the platen, the entire unit 10 may be lifted up and a documentsheet or book or the like placed over the platen manually. When thedocument handling unit is lowered, the belt 12 will overly the documentand prevent it from lifting out of focus above the platen. Thisalternative manual copying feature, in which the document belt 12 isstationary, is known in other vacuum belt document handling systems.Such manual copying may be utilized, for example, with documents whosesizes or conditions are not appropriate for automatic vacuum feeding bythe document belt. However, such manually placed documents, particularlyunusually small, or odd sized, or transparent, or very thin, documents,are ones which often have even more severe show-around or show-throughproblems than those which are feedable. That is, the copying of shadowsof vacuum apertures through or around documents is often moreobjectionable in the manual copying mode. This has been considered aserious disadvantage in the use of a vacuum document feeder incomparison to a fixed surface manual platen cover. It has even beenproposed to provide an alternative manual platen cover in place of thevacuum belt for the manual copying mode, but this obviously addscomplexity and cost. all of these problems have been eliminated by thepresent system.

In order to provide the desired completely unapertured and ungroovedcontinuous single belt surface over the platen for manual copying, thereare provided two cooperating features: an adequate spacing ofunapertured belt area 39 between at least two of the patterns 38, and ameans for automatically registering this area 39 over the platen whenthe copier is to be used for manual copying. For example, if the blankpitch 39 between vacuum apertures is on the order of 38 centimeters (fora platen of that dimensions) this 38 centimeter long segment of the beltmust be centered over the platen to avoid any exposure of any vacuumapertures 40. Note that, as described above, this is not the normalstopping position of the belt during automatic or semi-automaticdocument feeding. The normal stopping position is with one aperturedarea 38 overlying the platen. Thus, a separate and additional beltregistration mode is preferably provided. This separate registrationmode causes the document belt to advance or cycle by an additional oddincrement to move the vacuum apertured area 38 which was previouslyoverlying the platen out of the exposure station, and overlays theexposure station with an unapertured belt area 39. It has been foundthat this may be automatically actuated and controlled in various ways.One way is to have the belt drive automatically start, advance for thedesired pre-set distance, and stop automatically upon a switch beingactuated by the lifting of the document handling unit 10, since thedocument handling unit is lifted for manual copying. However, this wouldcause the belt to be moved slightly when the cover is lifted, whichmight startle the operator. Thus, it is preferable to have the beltautomatically advance into this manual copying position automatically inresponse to the termination of the automatic or semi-automatic documentfeeding of the belt. This can be accomplished by a simple timingarrangement which is a part of the controller or timing control 34. Thatis, when, after a time interval of a few seconds, or less, no additionaldocuments have been fed by the belt, e.g., the belt has not moved duringthis time period, then the belt will automatically shift from its normalstopping position (with the one vacuum apertured area 38 over theplaten) into its manual copying position with no apertured vacuum area38 over the platen.

The sensing of the belt position can be done with the same cursors orfiduciary position marks on the belt and sensors connected to a servodrive motor for the belt as previously described for the loadingregistration of the belt patterns 38 with the document. Alternatively, aseparate hole or mark in the belt, and/or separate sensor, can beutilized to sense whether the belt is in the proper manual copyingposition and stop the belt drive in that position. This can also be doneon machine start-up.

As a further alternative, it will be appreciated that a system may bedesigned in which, after each document is copied and ejected orrestacked, the belt is automatically stopped in the manual copyingposition so that the automatic or semi-automatic document feeding may beinterrupted at any time, even during a run, for immediate manual copyingwithout moving the belt. As another alternative, a separate button orswitch and/or drive could be provided to move the belt into the manualcopying position.

The above described arrangement of a vacuum belt with only two vacuumapertured areas 38 thereon is particularly desirable for the abovedescribed manual copying mode, as allowing a realtively short overallbelt length to provide a large unapertured area 39. However, it will beappreciated that the unapertured length 39 of the belt can be providedby increasing the overall belt length in various ways withoutnecessarily substantially increasing the overall size of the documenthandling unit. For example, as described, the rollers at opposite endsof the document belt may be spaced substantially beyond the edges of theplaten, so that a vacuum pattern may be spaced off of the platen eventhough it is still in the lower flight of the belt, i.e., in the platenoverhang area of the extended belt. Alternatively, larger belt supportrollers or multiple rollers or guides which provide convolutions orbights in the return belt flight may be provided to increase the overallbelt length. It has also been found, as discussed elsewhere herein, thatthe apertured areas 38 may be made considerably smaller by restrictingthem to only the lead edge areas of the smallest document, and this hasbeen established to provide satisfactory vacuum document retention withthe improved vacuum retention systems disclosed herein. This reductionof the area 38 of the vacuum apertures correspondingly increases theavailable unapertured pitch 39 therebetween without increasing theoverall belt length.

The system disclosed herein is adapted to handle a wide range ofdocument sizes and weights. The following table lists the more commomstandard document and copy sheets and their approximate sizes, whichvary with cutting accuracy, humidity, etc..

    ______________________________________                                        Common Standard Commercial Paper Sheet Sizes                                  Size Description                                                                              Size in Inches                                                                           Size in Centimeters                                ______________________________________                                        1.    U.S. Government                                                                              8 × 10.5                                                                          20.3 × 26.7                                    (old)                                                                   2.    U.S. Letter   8.5 × 11                                                                           21.6 × 27.9                              3.    U.S. Legal    8.5 × 13                                                                           21.6 × 33.0                              4.    U.S. Legal    8.5 × 14                                                                           21.6 × 35.6                              5.    U.S. Engineering                                                                             9 × 12                                                                            22.9 × 30.5                              6.    ISO* B5       6.93 × 9.84                                                                        17.6 × 25.0                              7.    ISO* A4        8.27 × 11.69                                                                      21.0 × 29.7                              8.    ISO* B4       9.84 × 13.9                                                                        25.0 × 35.3                              9.    Japanese B5    7.17 × 10.12                                                                      18.2 × 25.7                              10.   Japanese B4   10.12 × 14.33                                                                      25.7 × 36.4                              ______________________________________                                         *International Standards Organization                                    

As previously noted, with the present system, show-around of the vacuumapertures is prevented by insuring that any document which is imagedoverlies all of the apertures adjacent its edges. I.e., the vacuumapertures are all preferably located well inside of the document edgesso as to all underlie the document in the area being imaged. Thosevacuum apertures which must be outside of the area covered by a smalldocument will be sufficiently distantly spaced from the document edgesso as not to be imaged. This is enabled by the unique vacuum grooveconstruction which allows the vacuum from the apertures to be appliednot just in the local area of the apertures, but rather to be extendedalong the grooves under all, or substantially all, of the full dimensionof the document. If the smallest documents to be copied are, forexample, International Standard B5 sized sheets, all of the vacuum holescan be located within an area of that size (176×250 mm) and there willbe no holes visible to the copier lens when it is in its registeredposition. As indicated above, this is greatly assisted by having all ofthe vacuum holes in specific pattern areas 38 which are widely spacedbetween unapertured areas 39 around the belt's circumference, coupledwith a registration or timing means which insures that the documents areonly fed onto the document belt in registration with a hole pattern area38, i.e., each document is individually fed only as a pattern area 38approaches the proper position for infeeding of the document intoregistration therewith. Note that the document sheet may be driven intoregistration with the belt, or the belt may be driven into registrationwith the document. That is, the speed or position of either the documentor the belt may be controlled by the conventional drives for either,which may be suitable mechanical systems or servo-motor driven.

For a good capture of the lead edge of the document, this registrationand feeding is preferably arranged so that, as illustrated by the dashedline document outline 23 in FIG. 2, the lead edge of the documentextends only a few millimeters beyond the first or leading apertures 40in the pattern 38. With the transverse grooves illustrated here, thisalso means that the lead edge of the document extends slightly beyondthe groove pattern. Thus, the leading and trailing edges of the documentmay completely cover the groove patterns and extend into ungrooved aswell as unapertured areas of the belt. With appropriate spacing of theareas 38, one document can be being acquired or loaded upstream of theplaten simultaneously with the imaging of the preceding document.

As additionally illustrated in FIG. 2, for assistance in acquisition ofthe lead edge, additional transverse extensions 36d of the grooves 36may be provided. These grooves 36d are integral and connecting shortextensions of the outer-most or lead edge groove 36. The grooves 36d areunapertured, but are provided with a vacuum by the apertures 40 in theircommunicating main groove 36, and act to extend the applied vacuum outto and slightly beyond the lead edge of the document to provide morepositive holddown of the lead edge. However, this is an optionalfeature. These groove extensions 36d have the same smooth and shallowangle and light reflecting characteristics as the main grooves 36 so asto be effectively optically invisible to the copier.

It is important to note that in a system as described above, where thedistance between the vacuum belt and the platen is within the opticaldepth of field of the optical system of the copier, that the documentdoes not have to be held flat against the document belt to be in focus.Thus, even if only the lead edge area of the document is positivelyvacuum gripped by the belt, or if less than half of the document widthin the case of a large document is positively gripped by a vacuum area,the remainder of the document can only sag or move away from the beltuntil it contacts the platen, and will be pulled across the platen bythe vacuum gripped areas of the same sheet with relatively low friction,and will still be maintained within the optical depth of field forcopying. It is only necessary that the total vacuum force applied to thedocument be sufficient to prevent the document from slipping on the beltonce it is acquired and registered thereon.

The present system allows an effective vacuum holding force to beprovided with low pressures and low air flow rates, thus requiring muchlower power, and also allowing a lower volume (smaller) vacuum manifoldbehind the belt. The total number of vacuum apertures required isgreatly reduced. The hole diameters and their total number are smallenough such that the manifold pressure will not significantly drop evenif all of the vacuum holes are exposed, yet the holes need not be sosmall as to have significant clogging problems.

Considering now the vacuum manifold 18, to further reduce both thevacuum requirements and the potential show-around print-out of vacuumholes even if they are exposed (uncovered), as an alternative, themanifold plate 20 may be only apertured in the actual document imagingarea of the smallest document to be imaged. The manifold plate 20 has awhite, light reflective, surface. As the apertured areas of the beltpass over the unapertured areas of the manifold, they may have a lightreflective bottom manifold surface 44 under the apertures 40, eventhough the apertures 40 are provided with a vacuum. This feature isillustrated in the enlarged cross-sectional views of FIGS. 3 and 4, andthe broken away belt area 41 of FIG. 2, where the manifold plate 20 isexposed (for illustration purposes only). This feature helps reduce thepotential for printout of the holes 40. The manifold plate 20 containsspaced vacuum apertures 42. These apertures 42 here are pneumaticallyconnected (open into) spaced grooves 43 recessed in the outer manifoldsurface abutting the back of the belt. These grooves 43 in the manifoldsurface are oriented transversely of the grooves 36 in the belt, but arealigned with the holes 40 in the belt to apply vacuum thereto. The beltholes 40 are in linear rows in the direction of belt movement alignedwith corresponding manifold grooves 43. The grooves 43 in the manifoldmay be unapertured outside of the smallest document imaging area, butextend the full length of the manifold plate 20. Thus, the grooves 43can communicate the vacuum through the manifold plate to all of theholes 40 at any desired belt position, yet still provide a lightreflective surface 44 under the holes 40. The surface 44 is provided bythe unapertured bottom of the grooves 43. In other words, similarly tothe pattern of vacuum apertures 40 in the belt 12 itself, theseapertures 42 in the manifold plate 20 can be restricted to specificminor areas of the manifold which will not normally be exposed to copieroptics, and the grooves 43 can extend a substantial distance beyond thelast of these apertures across the manifold surface to apply the vacuumto whatever areas of the belt it is desired to apply a vacuum. However,even if apertures 42 are provided along the grooves 43 under other beltareas, most of them will still normally be out of alignment with theholes 40, if the hole 42 spacings are different from the hole 40spacings in the direction of belt movement as well, i.e., a "vernier"non-alignment.

Additionally, or alternatively, as illustrated in FIG. 5, alternativeapertures 46 in an alternative manifold plate 47 may be positioned,angled or otherwise constructed to communicate only with the outsideedges of the grooves or slots 48 in the manifold plate. As in thegrooves 43 of the embodiment of FIGS. 3 and 4, these grooves or slots 48in FIG. 5 are preferably substantially wider than the overlying beltapertures 40, so as to allow for some lateral misalignment or movementof the belt, and unrestricted airflow. Thus, the positioning of thesemanifold aperture 46 laterally off-set, as in FIG. 5, or otherwise, fromthe outside edges of the belt apertures 40 prevents any of the manifoldapertures 46 from ever directly underlying any of the belt apertures 40,thus insuring a light reflective "bottom" 49 for every exposed aperture40 in the belt. The grooves 48, and the grooves 43, are preferablyclosely spaced (within less than 2 millimeters, for example), of theouter surface opening of the apertures 40 on the belt imaging surface37, so that the reflective surfaces 49 or 44 closely underly theapertures 40 and optically "wash out" part of what would otherwise be asolid dark spot on the copy sheet corresponding to document illuminationgoing into the holes 40 and not being reflected back out.

The grooves 43 or 48 in the manifold can be machined or formed therein,and the holes 42 or 46 drilled through the grooves, or the manifoldplate 20 can be monolithically formed by plastic casting, molding or thelike, (grooves, hole patterns and all). Alternatively, the manifoldplate 20 could be formed by overlaying and securing two separate platestogether, one apertured and one grooved. As indicated, these grooves 43or 48 are preferably made substantially larger in cross-sectional areasthan the grooves 36 in the belt 12, so as to provide relativelyunrestricted airflow therethrough between the interior of the vacuummanifold and the vacuum apertures 40 in the belt. It will also beappreciated that the apertures 42 or 46 through the manifold plate 20 or47 can be in the form of slots or oval apertures to increase theireffective opening areas yet enable a decrease in their lateraldimensions or assist in reducing the overlapping of a manifold hole witha vacuum belt hole.

To express the above in another way, the abovedescribed system providesa light reflective surface 44 or 49 closely spaced below the bottoms ofthe apertures in the vacuum belt wherever desired, by normallyoff-setting most of the apertures in the manifold from the apertures inthe belt but providing pneumatic communication between the manifoldinterior and the belt apertures. This vacuum flow path is throughunapertured grooves or the like internally of the manifold, so as toprovide an unapertured planar light reflective surface closelyunderlying the belt apertures.

It should also be noted that there is only a very small area of vacuumapplication to the back of the belt, in the limited areas of the grooves43 or 48, since they are only needed in the corresponding limited "band"areas of the holes 40. This significantly reduces the frictional dragbetween the manifold plate 20 and the belt.

Turning now in further detail to the structure and function of thepreferred belt 12 grooves 36, as previously indicated each grooveprovides an independent vacuum holddown which is not affected by theopening (non-converage by a document) of any of the other vacuumgrooves. That is, even if directly adjacent grooves are not covered by adocument due to a dog ears, holes, tears, irregular sizes, ormis-registration of the document, the vacuums in the other adjacentgrooves are not affected. All of the other, non-affected, grooves canprovide a full vacuum force capture of the document. There is nopressure loss between the grooves. Each groove is separated from theothers by a substantial area of the planar surface 37 of the belt.

By having the grooves 36 all, or primarily, run laterally, transversethe direction of movement of the belt, as in FIG. 2, it has been foundthat a substantial improvement can be provided in the vacuum "capture"of the lead edge area of the document, independently of the size of thedocument, as opposed to having the grooves run or extend in thedirection of movement of the document. With such transverse or lateralgrooves, several grooves can act independently to capture the lead edgeof the document by applying a vacuum force along the full groove areasextending across the full width of the document. If, due tomis-registration or lead edge curl of the document or the like, thefirst of these lateral grooves is not covered by the document, thedocument will still be captured by the subsequent grooves only a fewmillimeters further downstream of the lead edge of the document, andtheir vacuum holding force is not affected by the failure to capture thedocument with the first or immediately subsequent grooves. Forming thegrooves in the belt parallel to the lead edge area of the document hasbeen found to provide an approximately 3 to 1 higher holddown force forthe lead edge area of the document in comparison to circumferential beltgrooves.

It has further been found that improved vacuum document holdingcharacteristics can be provided by a specific relationship between theopening area of the vacuum holes 40 and the cross-sectional area oftheir belt grooves 36. Specifically, it has been found that by providinga much higher resistance to the air flow through or along a groove 36itself as compared to the airflow through the apertures 40 in thatgroove, that improved vacuum retention can be provided. This isprovided, by having the total area of all of the vacuum holes 40 in eachhole area (aperture band or group) each groove 36 to be more thanapproximately 5 to 6 times greater than the total cross-sectional areasof that groove 36 on both sides of the hole area (the two air inflowareas to a covered groove area). This ratio is greatly exceeded by thevery shallow grooves and relatively large holes disclosed in theabove-described specific dimensional examples. Thus, with the largespacing between the two 5 aperture groups in FIG. 2, they are alsopneumatically independent of one another even within the same groove.

This relatively small cross-sectional area of the shallow groovesprovides a substantial restriction or pressure drop in the airflowthrough the grooves in the areas of the grooves covered by a document.This pressure drop in the groove increases the effective vacuum (reducedair pressure) under the document along each groove 36 beyond the area 38of apertures 40, even though part of the groove is not covered by thedocument, e.g., if part of the grooves is exposed by holes, dog ears(bent or missing corners), or tears in the document. This allows thegrooves to extend substantially out beyond the edges or sides ofnarrower documents, as illustrated in FIG. 2, and yet provide a highvacuum holddown force for these smaller documents even though air isbeing drawn in from the open groove ends which are extending beyond thedocument, without having to rely only on the Bernoulli effect from thevelocity of the air through the groove, and without having to rely onlyon a static vacuum provided in a groove which is fully pnematicallysealed by a document.

To express it another way, the drop in pressure in the groove under theouter edge areas of the document applies a higher percentage of thevacuum manifold pressure to the remainder of the groove underlying thedocument. The impedance of air flow through these restrictedcross-sectional area grooves also substantially reduces the airflow intothe apertures 40 which are overlaid by documents, even though the entiregroove is not covered. This substantially reduces the total air flowrequirements of the system since, as previously described, the vacuumapertures 40 are so arranged as to normally be covered by even thesmallest document to be copied. Yet, with this system of high air flowimpedance grooves, these same limited areas of apertures 40, in only theminor, small document, areas 38 of the belt, can provide high vacuumholddown forces over a much greater area for much larger documents byextending the same grooves, without additional holes 40, across the beltover the areas to be overlaid by the larger documents. This isaccomplished without significantly increasing the airflow or vacuumpressure requirements for smaller documents even though a highpercentage or major portion of the vacuum grooves are exposed(uncovered) by the small documents.

It should be noted, however, that the resistance to airflow along thebelt grooves 36 is very much lower than the resistance to airflowbetween adjacent grooves in the covered areas. Further, a substantiallylarger cross-sectional area of grooves than that disclosed above willstill provide effective vacuum holddown. By increasing the airflowthrough a larger groove a pressure drop will still occur, predominantlyat the edge of the document wherever the groove extends out beyond thedocument, since this is where the airflow first encounters a restrictionin entering the groove.

To summarize, with the disclosed system, vacuum apertures may beprovided in the belt which are spaced well inside of the edges of thesmallest document. This prevents any possibility of show-around oroptical exposure of these holes even if the document is mis-registeredor skewed, yet with the disclosed system, the area of applied vacuum canextend out to the edges of the document through the extendingunapertured portions of each groove, and without any correspondingincrease being required in the airflow. In face, since the effectivearea of the applied vacuum increases with larger documents covering moreof the groove length, and since the airflow decreases with largerdocuments due to the increased covered length of the grooves, the samelow power vacuum source will automatically provide an increased vacuumretention of larger documents to the belt without any increase in thepower being applied to the vacuum surface.

For initial acquisition or capture of the documents with a desired lowpower, low airflow, vacuum system the document sheets are initiallymechanically pressed or urged against the vacuum belt by an angularintersection (sheet beam strength) or with pressing rollers, belts, orthe like as in the above-cited U.S. Pat. No. 4,043,665. Once thedocument surface has been thus mechanically acquired, i.e., is overlyingany of the vacuum grooves, there is an almost immediate vacuum drop inthe grooves due to their very small volume and the relatively muchlarger cross-sectional areas of the apertures 40 therein. That is, thereis a relatively unrestricted vacuum application through the apertures 40to the groove once the groove is at least partially covered by thedocument in the area of the apertures 40. Thus, only a brief initialcontact is needed between any area of the document sheet and the belt toobtain vacuum acquisition of that area of the document, e.g., the linecontact of a roller 30 nip, and very low vacuum power is required tomaintain or hold the document thereafter. Assuming a normal relativelyhigh coefficient of friction of the belt surface 37, the staticfrictional forces between the belt and document are sufficient toprevent relative slippage once even a minor area of the document hasbeen acquired with this vacuum holddown.

Referring now to FIGS. 6, 7 and 8, there is shown therein a distinctlydifferent embodiment. FIG. 6 is a bottom view at the document imagingarea of one patterned area 64 of a different belt 60 overlying a portionof the vacuum manifold plate 62. As described above, the vacuum manifoldplate 62 contains vacuum grooves 63 for applying a vacuum to the limitedareas of vacuum apertures 70 of the vacuum belt 60. It will beappreciated that the pattern area 64 of the belt 60 illustrated here is,as with the embodiments described above, only a minor portion of thebelt, and that the majority of the belt may be both unapertured andungrooved, i.e., completely smooth. That is, the belt 60 preferablycontains only two or three of these patterned areas 64 widely spaced orpitched around the circumference of the belt 60 in the direction of beltmotion. For example, two areas 64 of 26 cm circumferential belt lengthseparated by two equal areas of 31 cm belt length.

The pattern 64 of belt 60 of FIGS. 6-8 is separated into differentvacuum areas for holding and imaging different standard sizes ofdocuments. Specifically it contains a first, central, area 67 for thesmallest size document, a second area 68 for larger documents and athird area 69 for the largest documents. The vacuum apertures 70 in thebelt 60 are provided as shown in 3 bands only in the first or centralarea 67, yet vacuum is provided from there to all of the other areas.Immediately surrounding the first area 67 on two sides 71a and 71b is afirst weir area 71. This narrow border pattern 71 is in turn surroundedon the same two adjacent sides, (for a corner registered document systemas here) by a second area 68. The second area 68 is correspondinglybordered on two sides and separated by the second weir areas 72a and72b. This is in turn bordered by the third area 69 which in turn isenclosed by the third weir area 73. Note that the weir areas mayslightly interconnect, i.e., be open at their intersecting corners tointerconnect (continue) the document vacuum areas 67, 68, and 69 there.

As illustrated in the cross-section of FIG. 7, the areas 67, 68 and 69are areas of relatively low airflow resistance or restriction betweenthe document and belt, (i.e., under the document) with relatively largebelt grooves 76 providing relatively open paths, whereas the weir areas71, 72 and 73 are areas of much higher airflow restriction provided bymuch smaller cross-sectional areas of openings or paths (grooves 77)under the document. It should be noted, however, that FIG. 7 is not toscale. The surface patterns thereon are magnified for drawing clarity.

Referring to FIG. 8, this is a small and highly enlarged section of thecentral area 67 of the belt 60 in a view corresponding to FIG. 6 plustwo orthogonal cross-sectional views of that same small section of thebelt. An exemplary vacuum aperture 70 is illustrated within this beltsegment. As may be clearly seen from the two cross-sectional views inFIG. 8, the surface configuration of the belt 60 in the area 67 (and 68and 69) is, in this example, smoothly and uniformly sinusoidal on bothorthogonal axies. Thus, this surface configuration provides vacuumgrooves 76 in both directions or both axies of the belt surface.However, the surface patterns of any of the areas are not limited tothis example. These vacuum grooves 76 unrestrictedly distributed underthe document, i.e., with little or no vacuum pressure drop, the vacuumapplied through the apertures 70 under the document, while the documentis held or spaced above the apertures 70 and most of the grooves 76 bythe corresponding smooth "bumps" or tops of hills 74 evenly spacedbetween the intervening grooves or valleys 76 in this pattern.

Referring now to the intervening weir areas 71-73, in contrast, as shownin FIG. 7, these provide airflow restrictive passageways around andbetween the respective document areas 67-69 for different sizeddocuments. Those weir areas which are overlaid by a document provide amuch smaller total cross-sectional groove area under the overlyingdocument, selected to provide a significant airflow restriction. Theweir areas may be provided by surface patterns similar to thatillustrated in FIG. 8, but much finer, so that the depth and width ofthe grooves between the bumps is several times smaller in the weirareas, so as to provide much smaller cross-sectional areas for thegrooves. However, as shown here instead, all the weir areas are one axisgrooves 77.

Examples of the surface pattern dimensions which may be used in thediscrete document holding areas 67, 68, 69 is a sinusoidal surface withthe period or pitch of the surface waves in both directions, (i.e., thedistance between adjacent peaks 74) being approximately 7.6 or 6.4millimeters, and a groove 76 depth of approximately 1 millimeter betweenthe top of the peaks 74 and the bottom of the grooves 76, and a groove76 radius of approximately 3.8 mm. In contrast the weir area surfacepattern dimensions are several times smaller. One example is imagegrooves 77 approximately 15 mm long, the same pitch as above, but a flatbottom groove with a depth of only 0.15 mm, 0.3 mm, and 0.66 mm forweirs 73, 72 and 71, respectively. The shorter weir sides 71b and 72bmay have slightly deeper (more open) grooves 77 than the longer weirsides 71a and 72a. The inner weirs are designed to provide less air flowrestriction than the outer weirs. The specific dimensions, will ofcourse, be selected to match the particular vacuum system and thedesired vacuum document holding force needed, depending on theco-efficient of friction between the belt and documents, the maximumdocument drag forces anticipated in the system, etc.

Note that the areas 67, 68 and 69 are preferably each formed slightlysmaller than a standard document size, respectively. For example, thecentral apertured area 67 may be slightly smaller than the smallestdocument to be copied, (i.e., ISO B5 and Japanese B5) (see the abovetable). The next area, one side of 68 plus 67, may be slightly smallerthan the dimensions of the next desired size, (e.g., U.S. 8×10 size),the third (adding the other side of area 68) underlying U.S. 8.5×11size, etc. The entire pattern 64 is preferably designed to theconfiguration disclosed in FIG. 6, which is generally to scale, toaccommodate all of the common standard document sizes listed above suchthat the trailing and inside edges of any of these documents, whenproperly registered, will be continuously in a weir area. This restrictsairflow from these document edges towards the apertures 70, andtherefore helps maintain a sufficient vacuum holding level under theentire document with a lower airflow. With such restricted airflow fromthe outermost overlaid weir patterns, the majority of the manifoldvacuum level (all of which is applied through apertures 70 in area 67)will be transmitted with some, but not an excessive, vacuum head lossout through the inner weirs and any gaps there-between to whichever ofthe other areas 68 or 69 is covered by a particular document. Theseareas 68 and 69 then distribute this vacuum over their own areas withlittle or no pressure drop. Further, since the weir groove 77 pattern inthe exposed weir areas around the document edges is much finer, andunapertured, show-around tendencies therefrom are further reduced.

With the vacuum belt 60 pattern of FIG. 6, the document would be loadedonto the belt 60 with its lead edge extending slightly (e.g., 4 mm)upstream of the upstream edge of the patterned area 64, i.e., slightlyabove the line 7--7 in FIG. 6. One side of the document would also beregistered to the belt 60 slightly overlying the left side of thepatterned area 64 in the corner registration system disclosed here.Thus, two sides of the document will be in completely unapertured andungrooved belt areas, and normally thereby provide vacuum seals at thosesides.

Another embodiment, with a different vacuum belt pattern of vacuumapertures and vacuum grooves, can have a "sunburst" or radiallyextending (and branching) vacuum groove pattern. Various other groovepatterns can be provided.

While the exemplary system described herein, particularly that of FIGS.2-4, is preferred, it will be appreciated that various otheralternatives, variations, modifications or improvements will be apparentto those skilled in the art from the teachings herein, and the followingclaims are intended to encompass all those falling within the truespirit and scope of the invention.

What is claimed is:
 1. In a document handling system in which documentsare moved with a vacuum belt to an imaging station of a copier where thedocument are illuminated for imaging against a light reflective documentimaging surface on a first side of said belt with a width greater thanthat of the document, and in which document handling system thedocuments are vacuum attracted toward said first side of said belt by anair flow applied from vacuum apertures in a light reflective vacuummanifold surface at the backside of said belt, which vacuum air flow iscommunicated from said manifold apertures through further apertures insaid vacuum belt which open on said first side of said belt, theimprovement wherein:said vacuum manifold surface at said backside ofsaid belt has elongated grooves slightly recessed in said manifoldsurface, said manifold surface grooves extend in the direction ofmovement of said belt spaced apart transverse the direction of movementof said belt, and relatively narrow in comparison to the overall widthof said vacuum belt, said vacuum apertures in said vacuum manifoldsurface open recessed within said grooves in said vacuum manifoldsurface; said vacuum belt apertures are in narrow bands of aperturessimilarly transversely spaced apart and similarly extending in thedirection of movement of said belt to generally overlie said grooves insaid vacuum manifold surface, said manifold surface grooves have asufficiently large cross-sectional area to provide relativelyunrestricted air flow from said manifold surface apertures along saidgrooves under said belt to said vacuum belt apertures.
 2. A documenthandling system according to claim 1, in which said manifold grooveshave light reflective bottom surfaces closely spaced below said backsideof said belt, and in which said vacuum aperture openings in said vacuummanifold surface are so positioned that at least most of them arenon-aligned and transversely spaced from said apertures in said vacuumbelt, so as not to underlie said vacuum belt apertures, and so that mostof said belt apertures closely overlie said light reflective bottomsurface of said grooves to provide a light reflective surface for saiddocument illumination in said imaging station to reduce the imaging ofvacuum belt apertures which are exposed in said imaging station.
 3. Adocument handling system according to claim 2, in which said vacuumapertures in said vacuum manifold surface are located only in limitedminor lengths of said grooves which underlie a portion of said imagingstation and which correspond to the limited area of the vacuum beltoverlaid by the smallest document to be moved by said vacuum belt tosaid imaging station, and wherein the unapertured major lengths of saidgrooves communicate said air flow from said limited apertured area ofsaid vacuum manifold surface for a substantial distance under said beltin the direction of document motion to other said vacuum apertures insaid belt which are substantially outside of said limited area, so thatall said other belt apertures outside of said limited apertured area ofsaid grooves are all closely underlaid by a continuous, completelyunapertured light reflective bottom surface of said grooves.
 4. Adocument handling system according to claims 1, 2 or 3, in which saidvacuum manifold surface outside of said grooves therein provides apneumatic seal along the edges of said grooves against the backside ofsaid vacuum belt to restrict the area of vacuum application to only theminor areas of the backside of said belt corresponding to the areas ofsaid grooves, to reduce friction between the backside of said vacuumbelt and said manifold surface.
 5. A document handling system accordingto claims 1, 2 or 3, in which the spacings between said vacuum aperturesin said vacuum manifold surface and the spacings between said vacuumapertures in said belt are non-integrally divisible different spacings,to provide a reduced coincidence of alignment of a vacuum manifoldsurface aperture with a vacuum belt aperture during movement of thebelt.
 6. A vacuum handling system according to claims 1, 2 or 3, inwhich said grooves in said vacuum manifold surface are substantiallywider than said corresponding overlying bands of vacuum apertures insaid belt, and wherein said vacuum apertures in said vacuum manifoldsurface are positioned toward the outside edges of said grooves inpositions which do not underlie any of the apertures in said vacuumbelt.
 7. A document handling system according to claims 1, 2 or 3, inwhich said vacuum belt has vacuum grooves on said first side of saidbelt communicating with said apertures in said vacuum belt, and whereinsaid vacuum grooves in said belt extend transversely of the direction ofsaid grooves in said manifold surface.